Supabase Row Level Security: How to Design Safer Policies
A practical explanation of Row Level Security policies, public content patterns and admin-only mutations for Supabase applications.
Start from the data access matrix
Before writing policies, write down who should be able to read, create, edit and delete each table. This turns vague security goals into explicit rules.
For example, published content may be public to read while unpublished content and all mutations remain restricted.
Prefer narrow policies over broad access
A policy should grant exactly the access needed for the operation. Broad authenticated access can accidentally expose records to users who should only see their own data.
Use the row values and authenticated identity together when the rule depends on ownership or role.
Test the failure cases
Good security work includes checking what an unauthorized user cannot do. Test public reads, anonymous writes, cross-user updates and unpublished records rather than only the happy path.
Keep policy names descriptive so the intent is easy to understand during future maintenance.